This application is based on European Patent Application No. 99830636.9 filed on Oct. 11, 1999, the content of which is incorporated hereinto by reference.
The present invention relates to a telescopic extension for an electric household appliance, such as a vacuum cleaner and the like.
Telescopic extensions for electric household appliances are known, said extensions comprising an inner tube and an outer tube sealingly slidable inside one another, a sleeve, a constraining means capable of locking together the inner tube and the outer tube, a thrusting slider engaging the constraining means through the action of resilient means, and actuating means operationally connected to the thrusting slider. In these extensions, the inner tube is provided with a row of notches of predefined shape, the sleeve is fixed to the outer tube and the constraining means and the thrusting slider are movably supported in said sleeve. The resilient means are also housed in said sleeve.
The thrusting slider acts on the constraining means, under the action of the resilient means, so as to force the constraining means inside a notch of inner tube and lock the inner tube inside the outer tube.
The actuating means, in turn, are capable of disengaging the thrusting slider from the constraining means so as to leave the constraining means free to move radially and come out of a notch of the inner tube. In this way the inner tube is disengaged from the outer tube and may be made to slide with respect to the outer tube so as to adjust the length of the extension.
In order to house said sleeve, some conventional telescopic extensions have an outer tube provided with a flaring (widened portion). An extension of this kind is described in EP-B1-0 293 518. The flaring of the outer pipe makes the extension somewhat voluminous and difficult to handle.
Alternatively, the locking and releasing slider is mounted in a projection of the sleeve seated in a niche formed in the outer tube by means of drawing.
Both these types of telescopic extension therefore require a controlled deformation of the outer tube. This type of processing technique has the following disadvantages:
it requires the use of proper machines,
it lengthens the working times,
it requires the use of costly materials having a high yield strength,
it produces a large amount of production rejections.
In order to overcome the drawbacks arising from having to deform the outer tube, EP-A2-0 601 620 proposes a telescopic extension having an outer tube with a cross-section of substantially constant diameter onto which a double sleeve is fastened. However, this extension is also fairly voluminous and costly because it comprises numerous components and requires fairly long assembly times.
DE-196 15 814 discloses a telescopic extension for a vacuum cleaner comprising an inner tube and an outer tube which slide inside one another and are made integral by means of one constraining element. Said outer tube has a flared portion and a sleeve is fastened to said flared portion and supports said inner tube. Said sleeve is provided with a longitudinal protrusion which engages a longitudinal groove of said inner tube and guides its sliding movements. Said longitudinal groove has a bottom portion provided with notches capable of housing said constraining element. An actuating slider is interposed between said flared portion of said outer tube and said sleeve and causes displacements of said constraining element for locking and unlocking said inner and outer tubes. Said actuating slider shows a locking retainer capable of keeping said constraining element in a locking position in a notch of the inner tube. Moreover, said actuating slider has a first hemispherical niche for housing said constraining element in a disengaging position and a second semicylindrical niche for housing a spring. Furthermore, said actuating slider is provided with a knob which is placed in a front edge of said outer tube in the longitudinal sliding direction of said actuating slider.
Owing to the presence of said first and second niche, said actuating slider has a fairly high thickness and said outer tube flared portion is provided with an enlarged tunnel-like seat capable of housing said actuating slider. Thus, said outer tube undergoes two deformations in order to form said flared portion and said tunnel-like seat. Therefore, the manufacture of said telescopic extension is troublesome and expensive. Moreover, the overall transversal dimension of said telescopic extension is large, unhandy and unaesthetic.
It is an object of the present invention to overcome the abovementioned drawbacks.
This object is achieved, according to the invention, by means of a telescopic extension for an electric household appliance comprising:
a) an inner tube and an outer tube sliding inside one another,
b) a sleeve fastened to said outer tube,
c) at least one first constraining means capable of locking together said inner tube and said outer tube,
d) a flat and long thrusting slider, engaging at least said first constraining means under the action of resilient means, and
e) actuating means operationally connected to said thrusting slider,
f) said inner tube being provided with a row of notches of predefined shape,
g) said outer tube having a cross-section of substantially constant diameter and having a lateral opening,
h) said first constraining means and thrusting slider being movably supported by said sleeve,
i) said thrusting slider acting on said first constraining means, through the action of said resilient means, so as to force said constraining means inside a first notch of said inner tube and lock said inner tube inside said outer tube;
j) said actuating means being capable of disengaging said thrusting slider from said first constraining means so as to leave said first constraining means free to move radially and come out of said first notch, releasing said inner tube from said outer tube and allowing said inner tube to slide with respect to said outer tube so as to adjust the length of said extension, characterized in that
k) said sleeve is arranged between said inner tube and said outer tube having a cross-section of substantially constant diameter,
l) said sleeve is provided with a longitudinal cavity and a recess formed on a bottom wall of said cavity,
m) said thrusting slider is housed in said longitudinal cavity and is retained radially by said outer tube,
n) said thrusting slider is provided with at least one first slot, and
o) said resilient means are housed in said first slot of said thrusting slider and engage said recess of said sleeve.
Preferably, said lateral opening of said outer tube extends as far as one end thereof and said sleeve has an external longitudinal projection which engages said opening so as to couple said outer tube with said sleeve and centre said outer tube with respect to said sleeve.
Advantageously, said lateral opening of said outer tube has dimensions such as to make accessible said thrusting slider housed in said longitudinal cavity of said sleeve.
Preferably, said thrusting slider is also provided with at least one second slot designed to receive said first constraining means when said slider moves longitudinally, in a first direction, and said first constraining means moves radially and comes out of said first notch of said inner tube.
In turn, said second slot has an inclined side which is designed to exert a radial thrust on said first constraining means.
Advantageously, said extension also comprises a second constraining means designed to engage a second notch of said inner tube, said thrusting slider being provided with a third slot designed to receive said second constraining means when said slider moves longitudinally, in said first direction, and said second constraining means moves radially and comes out of said second notch of said inner tube.
Preferably, said third slot has an inclined side which is designed to exert a radial thrust on said second constraining means.
Moreover, said thrusting slider is provided with a fourth and a fifth slot which are designed to receive said first and said second constraining means, respectively, when said slider moves longitudinally, in the opposite direction to said first direction, and said first constraining means and said second constraining means move radially, respectively, and come out of said first and said second notch, respectively.
Advantageously, said fourth and fifth slot have a respective side inclined in the opposite direction to that of said sides of said second and third slot.
Preferably, said thrusting slider is provided with a projecting, substantially perpendicular tongue.
Advantageously, said tongue of said thrusting slider emerges from said lateral opening of said outer tube so as to engage said actuating means.
Preferably, said tongue of said thrusting slider has undercuts and said actuating means consist of a pushbutton having a pocket provided with additional undercuts which snap-engage said undercuts in said tongue.
According to a variant, said actuating means consist of a ring nut provided with a bayonet joint which engages said tongue of said thrusting slider and with a relief on said outer tube so as to lock together said ring nut and said slider for the longitudinal movements and allow said ring nut to move longitudinally with respect to said outer tube.
Preferably, said sleeve is provided with a collar against which said end of said outer tube comes into abutment, said collar and said external projection having a thickness substantially equal to that of said outer tube such that it remains flush with said collar and said external projection.
Advantageously, said sleeve has an internal longitudinal overhang and said inner tube has a longitudinal groove with which said internal longitudinal overhang of said sleeve engages so as to centre said sleeve with respect to said inner tube.
Preferably, said longitudinal groove has a bottom wall provided with said notches, and said internal longitudinal overhang of said sleeve, which engages with said groove, is arranged underneath said longitudinal cavity which houses said thrusting slider.
The telescopic extension of the invention has the advantage of being extremely compact and particularly resistant to operating stresses, such as axial thrusts and torque.
Moreover, it may be assembled using a considerably simplified process which allows production times and costs to be reduced and which may be easily automated.
During the course of the present description and the claims, the expression xe2x80x9ctube having a cross-section of substantially constant diameterxe2x80x9d is used to indicate that the tube is without a deformed portion designed to house the sleeve wholly or partly. However, there may be deformations of the tube which have a different function.